This is a little different. It was well after the last glacial maximum but the glacial waters were still trapped in the prehistoric lakes like Lake Iroquois and

This is a little different. It was well after the last glacial maximum but the glacial waters were still trapped in the prehistoric lakes like Lake Iroquois and the Champlain Sea; the oceans rose once these lakes drained. The caves are inland and part of the limestone karst found throughout the Yucatán peninsula and Florida. Divers have been exploring these fresh water cenotes and the attached subterranean caves/rivers for a long time. The cenotes were an important part of Mayan culture but that occurred much more recently (i.e. not prehistoric). Salt water is not friendly to human artifacts. The cold fresh water in these systems is ideal to preserve them. This site seems like a very unique overlap in time and place. Quite a gift really.